Concerns regarding the viability of oil as a practical energy source continue to mount throughout the world whether brought on by resource scarcity, economic climate, or strained relations with entities in possession of oil reserves. Additionally, environmental issues associated with burning oil, such as air pollution and global warming, have further put the long-term viability of oil-based energy at question. As a result, alternative energies, such as nuclear power, solar power and wind power, have become the focus of increased use and evaluation by a multitude of governments and private entities throughout the world. It is believed by many that nuclear power provides the only energy source that can realistically meet the energy needs of industrialized nations.
The fundamental concern with the use of nuclear power has been related to the disposal of the spent nuclear fuel rods after they have been depleted in the nuclear reactor. As a result, the industry continues to search for new and improved methods and systems for storing, transporting and transferring spent nuclear fuels rods. These systems must be meet carefully regulated government safety mandates regarding radiation containment, structural integrity, adequate ventilation, etc.
An example of an existing ventilated storage system (and its associated method of storage and transfer) are disclosed in U.S. Pat. No. 7,330,526 (the '526 patent), issued Feb. 12, 2008 to Krishna P. Singh, one of the present inventors of the present application. Another suitable existing ventilated storage system (and its associated methods of storage and transfer) are disclosed in U.S. Pat. No. 7,068,748 (the '748 patent), issued Jun. 27, 2006 to Krishna P. Singh. The entireties of these applications are incorporated by reference herein. The systems and methods disclosed in the '526 and '748 patent are extremely useful and effective as they are designed to utilize the naturally existing radiation shielding properties of the ground to increase the radiation containment abilities of the systems while still affording adequate ventilation. While these designs are adequate, and even optimal, in many circumstances, these systems can not be universally used at all existing spent nuclear fuel storage sites, whether temporary or long-term, for a number of factors. Such factors may include existing capital equipment at the site, geographic layout, climate, space limitations, etc.
For obvious reasons, storage space at any storage site, whether temporary or long-term, is at a premium. Thus, one of the major considerations in any storage system is the maximization of storage capacity per area (or volume). To this extent, storage systems that provide storage cavities in an arrayed configuration have been developed. An example of an arrayed underground storage system is disclosed in United States Patent Application Publication 2006/0251201, published Nov. 9, 2006, to Krishna P. Singh.
Another above-grade arrayed storage system is also disclosed in UK Patent Application Publication GB2337772A, published Jan. 12, 2999, to Blackbourn et al. The Blackbourn system for storing canisters containing hot spent nuclear fuel or waste. The Blackbourn system stores the canister in respective chambers of a vault and are air-cooled by natural convection. The vault is constructed from pre-cast concrete sections, assembled on-site and secured together by poured concrete. Each chamber has a stainless steel liner defining inner and outer annular spaces between the hot wall of the canister and the concrete wall of the chamber through which cooling air flows by convection. Air from the outer space discharges via exit vents cast into the concrete, air from the inner space via gap between metal lid and flanges. The liner shields the concrete from direct thermal radiation from the hot canister wall and provides additional surfaces from which heat can be lost by convection. The inner metal-lined air path prevents very hot air from coming into direct contact with concrete. Slots allow hot air to discharge via one of the exit vents in the event of blockage of the other. The concrete walls themselves are cooled by further ducts formed as an integral part of the pre-cast structure.
While the Blackbourn system is a suitable structure, it suffers from a number drawbacks. For example, the concrete structures between the separated and isolated storage chambers is susceptible to being subjected to overheating and eventual degradation. Moreover, by surrounding each chamber with a concrete structure, additional space is occupied per chamber, thereby increasing the overall size of the vault without achieving increased storage capacity.
Additionally, by designing the Blackbourn vault so that each storage chamber acts as its own independent ventilated system, the proper ventilation of any single chamber can be easily choked off by the blocking of only a few inlet ducts. Finally, the Blackbourn system does not accommodate thermal expansion of its metal parts adequately, thereby exposing certain components to great stresses and increasing the possibility of eventual fatigue and failure.